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app.py

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+import io
+import cv2
+import numpy as np
+from PIL import Image
+from filters import *
+import streamlit as st
+
+
+# Generating a button to download the image file.
+def download_image_button(img, filename, text):
+    buffered = io.BytesIO()
+    img.save(buffered, format="JPEG")
+    img_bytes = buffered.getvalue()
+
+    # Using st.download_button to handle the download
+    st.download_button(label=text, data=img_bytes, file_name=filename, mime="image/jpeg", use_container_width=True)
+
+
+# Set title.
+st.title("Artistic Image Filters")
+
+# Upload image.
+uploaded_file = st.file_uploader("Choose an image file:", type=["png", "jpg"])
+
+if uploaded_file is not None:
+    # Convert the file to an opencv image.
+    raw_bytes = np.asarray(bytearray(uploaded_file.read()), dtype=np.uint8)
+    img = cv2.imdecode(raw_bytes, cv2.IMREAD_COLOR)
+    input_col, output_col = st.columns(2)
+    with input_col:
+        st.header("Original")
+        # Display uploaded image.
+        st.image(img, channels="BGR", use_column_width=True)
+
+    st.header("Filter Examples:")
+
+    # Display radio buttons for choosing the filter to apply.
+    option = st.radio(
+        "Select a filter:",
+        (
+            "None",
+            "Black and White",
+            "Sepia / Vintage",
+            "Vignette Effect",
+            "Pencil Sketch",
+        ),
+        horizontal=True,
+    )
+
+    # Define columns for thumbnail images.
+    col1, col2, col3, col4 = st.columns(4)
+    with col1:
+        st.caption("Black and White")
+        st.image("filter_bw.jpg")
+    with col2:
+        st.caption("Sepia / Vintage")
+        st.image("filter_sepia.jpg")
+    with col3:
+        st.caption("Vignette Effect")
+        st.image("filter_vignette.jpg")
+    with col4:
+        st.caption("Pencil Sketch")
+        st.image("filter_pencil_sketch.jpg")
+
+    # Flag for showing output image.
+    output_flag = 1
+    # Colorspace of output image.
+    color = "BGR"
+
+    # Generate filtered image based on the selected option.
+    if option == "None":
+        # Don't show output image.
+        output_flag = 0
+    elif option == "Black and White":
+        output = bw_filter(img)
+        color = "GRAY"
+    elif option == "Sepia / Vintage":
+        output = sepia(img)
+    elif option == "Vignette Effect":
+        level = st.slider("level", 0, 5, 2)
+        output = vignette(img, level)
+    elif option == "Pencil Sketch":
+        ksize = st.slider("Blur kernel size", 1, 11, 5, step=2)
+        output = pencil_sketch(img, ksize)
+        color = "GRAY"
+
+    with output_col:
+        if output_flag == 1:
+            st.header("Output")
+            st.image(output, channels=color)
+            # fromarray converts cv2 image into PIL format for saving it using download button.
+            if color == "BGR":
+                result = Image.fromarray(output[:, :, ::-1])
+            else:
+                result = Image.fromarray(output)
+                
+            # Display the download button with the text "Download Output"
+            download_image_button(result, "output.jpg", "Download Output")
+        else:
+            st.header("Output")
+            st.image(img, channels=color)
+            

filters.py

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+import cv2
+import numpy as np
+import streamlit as st
+
+
+@st.cache_data
+def bw_filter(img):
+    img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
+    return img_gray
+
+
+@st.cache_data
+def vignette(img, level=2):
+    height, width = img.shape[:2]
+
+    # Generate vignette mask using Gaussian kernels.
+    X_resultant_kernel = cv2.getGaussianKernel(width, width / level)
+    Y_resultant_kernel = cv2.getGaussianKernel(height, height / level)
+
+    # Generating resultant_kernel matrix.
+    kernel = Y_resultant_kernel * X_resultant_kernel.T
+    mask = kernel / kernel.max()
+
+    img_vignette = np.copy(img)
+
+    # Apply the mask to each channel in the input image.
+    for i in range(3):
+        img_vignette[:, :, i] = img_vignette[:, :, i] * mask
+
+    return img_vignette
+
+
+@st.cache_data
+def sepia(img):
+    img_sepia = img.copy()
+    # Converting to RGB as sepia matrix below is for RGB.
+    img_sepia = cv2.cvtColor(img_sepia, cv2.COLOR_BGR2RGB)
+    img_sepia = np.array(img_sepia, dtype=np.float64)
+    img_sepia = cv2.transform(
+        img_sepia, np.matrix([[0.393, 0.769, 0.189], [0.349, 0.686, 0.168], [0.272, 0.534, 0.131]])
+    )
+    # Clip values to the range [0, 255].
+    img_sepia = np.clip(img_sepia, 0, 255)
+    img_sepia = np.array(img_sepia, dtype=np.uint8)
+    img_sepia = cv2.cvtColor(img_sepia, cv2.COLOR_RGB2BGR)
+    return img_sepia
+
+
+@st.cache_data
+def pencil_sketch(img, ksize=5):
+    img_blur = cv2.GaussianBlur(img, (ksize, ksize), 0, 0)
+    img_sketch, _ = cv2.pencilSketch(img_blur)
+    return img_sketch

requirements.txt

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+opencv-python==4.10.0.84
+streamlit==1.38.0